Serum urate and probability of dopaminergic deficit in early "Parkinson's disease".

The objective of this study was to investigate whether higher levels of urate, an antioxidant linked to a lower likelihood of developing Parkinson's disease, is also a predictor of having a dopamine transporter brain scan without evidence of dopaminergic deficit. In a cross-sectional study of 797 mildly affected, untreated parkinsonian subjects diagnosed with early Parkinson's disease in the Parkinson Research Examination of CEP-1347 Trial, we investigated the relationship at baseline between serum urate and striatal dopamine transporter density, determined by single-photon emission computed tomography of iodine-123-labeled 2-β-carboxymethoxy-3-β-(4-iodophenyl)tropane uptake. A scan without evidence of dopaminergic deficit was defined as lowest putamen iodine-123-labeled 2-β-carboxymethoxy-3-β-(4-iodophenyl)tropane > 80% age-expected putamen dopamine transporter density. The odds of having a scan without evidence of dopaminergic deficit rose across increasing quintiles of urate level, with an age- and sex-adjusted odds ratio of 3.2 comparing the highest to the lowest urate quintile (95% confidence interval, 1.5-7.2; P for trend = .0003), and remained significant after adjusting for potential confounding factors. The association was significant in men but not women, regardless of whether common or sex-specific quintiles of urate were used. Higher levels of urate were associated with a greater likelihood of a scan without evidence of dopaminergic deficit among subjects with early untreated parkinsonism in the Parkinson Research Examination of CEP-1347 Trial. The findings support the diagnostic utility of urate in combination with other determinants.